The present invention relates to a control or positioning element which is an electrically actuated transducer formed of a plurality of lamellae of piezoelectric material. The lamellae are combined to form a packet. The length of the lamellae are at least five times as great as a thickness of the individual lamella and the lamellae all have a substantially same thickness. A length of the lamellae from end to end shortened or lengthen upon application of an electrical voltage depending on the operational sign of the voltage and the polarization of the material.
Known from the prior art is a control or positioning element constructed as a piezo motor for the control of the valves. Specifically, a piezo-electrical transducer comprised of a lamella packet is known with which piezoelectric generated changes of length given the exertion of a force are achieved.
As a rule, a transducer for such a piezoelectric control or positioning element comprising piezo ceramic and, in particular, of a stack of wafers lying on top of one another which are respectively polarized in the direction of their thickness and are electrically connected parallel to the polarization. So as not to destroy the impressed polarization of the piezo-ceramic during operation, the electrical voltage is usually connected with a polarity which promotes the polarization of the ceramic. In the case of such a disk, this means that when such an electrical voltage is applied, it expands in the direction of its thickness, i.e. the entire stack undergoes an increase in height. Thus, pressure can be provided by the control or positioning element when the electrical voltage is operationally applied. However, given the same relationship between the polarization direction and polarity of the voltage to be applied, no increase in the length of the packet (the length measured at right angles to the direction of the thickness of the individual lamella) occurs, given the afore-mentioned packet comprising piezo ceramic lamellae. Rather, a shortening of the length occurs because the d.sub.31 effect results here. This d.sub.31 effect, moreover, has the disadvantage that the change in length of the lamella packet amounts to only approximately 1/2 of the enlargement of the thickness of the lamella packet which simultaneously occurs. If, however, the lamella packet is made a multiple which is longer than the thickness of an individual lamella of the packet, then one obtains a change of length that is nonetheless comparatively much greater than a pellet stack of the same length.